1. Field of the Invention
The invention in general relates to the field of medical, dental and therapeutic lavage, and more particularly to a mechanized lavage system having a fluid pump driven by an electric motor.
2. Description of the Prior Art
Lavage, or the washing of tissue, is perhaps as old as medicine itself. In the early years it consisted of the application of fluid, generally a liquid such as water, to tissue to wash away dirt or debris. In more modern times, it has become more important, and more thorough, due to an awareness of bacteria and other organisms that may cause infection. In the last several decades, mechanized lavage systems have become common.
Before proceeding to the discussion of prior art mechanized devices it will be useful to clarify terminology. The word "lavage" is used ambiguously in the literature, sometimes referring to a pulsating stream type washing or therapy, sometimes referring to a stream type of washing, and sometimes also including an aspiration function. In this document, unless the context clearly indicates otherwise, "irrigation" shall mean the stream type of washing "pulsatile lavage" shall mean the pulsating type of washing or therapy, and the word "lavage" shall mean the broadest sense of the term, referring to any one of, or combinations of, irrigation, pulsatile lavage, and aspiration.
U.S. Pat. No. 3,540,437 issued to Seymour Troy and U.S. Pat. No. 4,278,078 issued to William E. Smith, illustrate lavage systems in which the fluid stream for irrigation or pulsatile lavage is produced by a reciprocating pump. The former patent gives no indication of the type of motor which may be used for driving the reciprocating pump, while the latter patent discloses a rotary gas-driven motor as the pump driving means. It appears that these prior art reciprocating pump systems have not been very successful; an analysis of the system of U.S. Pat. No. 3,540,437 indicates that the pulsation produced would be either very weak or nonexistent, while it appears that the system of U.S. Pat. No. 4,278,078 would be very inefficient.
U.S. Pat. Nos. 3,912,168 issued to Keith M. Mullins et al and 3,993,054 issued to Gordon Arthur Newman, disclose lavage systems incorporating a peristaltic pump driven by a rotary electric motor. These peristaltic type systems in general appear to have been more successful than the above-cited reciprocating systems. However, it is noted that none of these systems appear to be frequency controlled. Further, it appears that the only volume controls disclosed in any of the lavage systems are throttle type controls, which are inherently inefficient. Despite these limitations, the peristaltic motor, at the time of the conception of the present invention has been the motor of choice in lavage systems, due to the small size of the lavage systems using such motors and the easy replaceability, sterilizability and the disposability of its pumping chamber. These two features are essential for commercial success of a medical, dental or therapeutic lavage system.
Up to the present time, moving coil electrical motors have been thought to be unsuitable for medical, dental and therapeutic lavage systems Generally, moving coil linear motors have been associated with functions requiring rapid response and small forces. Typical applications have been loudspeakers, or the movement of magnetic heads or pens in information processing systems See for example U.S. Pat. No. 3,917,987 issued to Yuji Inoue. Whenever moving coil type linear motors have been used for functions requiring a force as significant as required in a lavage system, very large motors have been designed. See, for example, U.S. Pat. Nos. 524,044 issued to Frank W. Merritt et al and 3,863,082 issued to Donald H. Gillott et al. The latter patent relates to a linear motor for use in a respirator requiring forces on the same order generally required for lavage systems. The size of the motor disclosed is about 14 inches long by 12 inches in diameter. The support system, drive system and cooling system of the motor of course would add considerably to the size. Thus any person skilled in the art of lavage systems would immediately reject such a motor for use in this field. The only disclosure known to the applicant which suggests the use of a small moving coil linear motor for fluid pumping purposes is
U.S. Pat. No. 2,669,937 issued to Shelly Presentey. However, the motor disclosed is clearly unsuitable for use in a lavage system. Moreover, the patent does not appear to disclose an actual use in any fluid pumping function, Further, the disclosure explicitly calls for elimination of all mechanical members such as shafts, journals, bearings and the like, which, as will be seen below, is directly contrary to the present invention.
Linear motors having stationary coils and moving magnets have apparently been used for pumping liquids. See, for example U.S. Pat. Nos. 3,423,983 issued to A. R. Keistman et al, 4,101,950 issued to Donald L. Hager et al, and Re. 20,510 issued to H. V. Green. Each of these patents is used for a function requiring considerably less force and lower usage requirements than required in a lavage system. Thus up to the present time no linear motor, either of the moving coil type or the moving magnet type, have ever been used in a lavage system.